It is known within geodetic surveying, or geodesy, to measure distances and angles by using electrooptical methods to determine the positions of measuring points in a relevant coordinate system. In one conventional method, an electrooptical distance measuring instrument (EDM) transmits a modulated light beam of infrared light, which is reflected from a prism of cubical configuration placed on the target point for the purpose of taking measurements. The light reflected by the prism is received and phase-detected, thereby enabling the distance to be determined with great accuracy. The vertical angle and horizontal direction to the target point can also be determined electrically or electrooptically. It is known to permit the measuring instrument to take repeated measurements and to continuously determine the position of a moving target, where the measuring instrument is directed onto the target manually.
It is also known for a measuring instrument to track or follow a target automatically with the aid of a servo drive controlled by a signal transmitted from or reflected by the target.